Mpls Traffic Engineering for Point-To-Multipoint Label Switched Paths

1. A method in a source edge router connected to a source, comprising the steps of: identifying a plurality of receivers that are requesting to receive data from the source in a session; sending a set of one or more PATH messages to one or more nodes downstream of the source edge router to signal a plurality of separate point-to-point label switched paths (LSPs) between the source edge router and a plurality of receiver edge routers associated with the plurality of receivers, wherein each one of the set of PATH messages includes a same identifier of a point-to-multipoint (P2MP) LSP that includes a session object that contains a tunnel identifier and a P2MP identifier; and receiving, from each of the one or more nodes downstream of the source edge router, a set of one or more RESV messages, wherein each one of the received RESV messages includes the identifier of the P2MP LSP and a label allocated by that downstream node that is to be used by the source edge router when sending traffic of the P2MP LSP to that downstream node.

2. The method of claim 1 , further comprising the step of: creating a mapping of an IP address associated with the P2MP LSP and the one or more labels specified in the set of received RESV messages.

3. The method of claim 2 , further comprising the steps of: identifying another receiver that is requesting to receive data from the source in the session; sending a PATH message to signal a point-to-point LSP for the another receiver, wherein the PATH message includes the identifier of the P2MP LSP; receiving a RESV message that includes the identifier of the P2MP LSP and a label; responsive to determining that the label specified in the RESV message is not already associated with the P2MP LSP, adding that label to the mapping of the IP address associated with the P2MP LSP.

4. The method of claim 1 , further comprising the step of: prior to sending the set of PATH messages, computing a separate point-to-point LSP between the source edge router and each of the plurality of receiver edge routers.

5. The method of claim 4 , wherein the separate point-to-point LSPs are computed to share resources where possible as determined by an IP routing protocol with Traffic Engineering (TE) extensions.

6. The method of claim 2 , further comprising the steps of: determining that one of the plurality of receivers is to be removed from the session; sending a PATH TEAR message to the one of the set of downstream nodes to reach the receiver that is to be removed from the session, wherein the PATH TEAR message identifies a point-to-point LSP to remove and includes the identifier of the P2MP LSP to cause the point-to-point LSP for the receiver to be removed from the P2MP LSP.

7. The method of claim 6 , further comprising the step of: responsive to determining that the one of the set of downstream nodes is involved only in a route to the receiver being removed, removing the label allocated by that downstream node from the mapping of the IP address associated with the P2MP LSP.

8. A method in a core router in a Multiprotocol Label Switching (MPLS) network, comprising the steps of: receiving a set of one or more first PATH messages from an upstream node, wherein the set of first PATH messages identify at least a portion of a first point-to-point label switched path (LSP) between a source edge router and a first receiver edge router and identify at least a portion of a second point-to-point LSP between the source edge router and a second receiver edge router, wherein the set of first PATH messages each includes a same identifier of a point-to-multipoint (P2MP) LSP that includes a session object that contains a tunnel identifier and a P2MP identifier; sending a second PATH message to a first downstream node on the first point-to-point LSP, the second PATH message including the identifier of the P2MP LSP; sending a third PATH message to a second downstream node on the second point-to-point LSP, the third PATH message including the identifier of the P2MP LSP; receiving, from the first downstream node, a first RESV message responsive to the second PATH message, the first RESV message including the identifier of the P2MP LSP and a first label allocated by the first downstream node; receiving, from the second downstream node, a second RESV message responsive to the third PATH message, the second RESV message including the identifier of the P2MP LSP and a second label allocated by the second downstream node; allocating a third label to be used by the upstream node when transmitting packets for the P2MP LSP to the core router; mapping the third label with the first label and the second label to enable the core router to replicate packets that are received from the upstream node that are labeled with the third label, send each replicated packet to the first downstream node being labeled with the first label, and send each replicated packet to the second downstream node being labeled with the second label; and sending a set of one or more third RESV messages to the upstream node responsive to receiving the first RESV message and the second RESV message, wherein the set of third RESV messages each includes the identifier of the P2MP LSP and the third label.

9. The method of claim 8 , further comprising the steps of: receiving a packet from the upstream node labeled with the third label; labeling the packet with the first label; sending the packet labeled with the first label to the first downstream node; labeling the packet with the second label; and sending the packet labeled with the second label to the second downstream node.

10. The method of claim 8 , wherein the upstream node is the source edge router attached to a source.

11. The method of claim 8 , wherein the upstream node is another core router.

12. The method of claim 8 , further comprising the steps of: receiving a fourth PATH message from the upstream node, wherein the fourth PATH message identifies at least a portion of a third point-to-point LSP between the source edge router and a third receiver edge router, wherein the fourth PATH message includes the identifier of the P2MP LSP, and wherein a path of the third point-to-point LSP shares a same link between the core router and the first downstream node; sending a fifth PATH message to the first downstream node, wherein the fifth PATH message includes the identifier of the P2MP LSP; receiving, from the first downstream node, a fourth RESV message responsive to the fifth PATH message, the fourth RESV message including the identifier of the P2MP LSP and the first label; sending a fifth RESV message to the upstream node responsive to receiving the fourth RESV message, wherein the fifth RESV message includes the identifier of the P2MP LSP and the third label.

13. An apparatus, comprising: a set of one or more processors in a source edge router connected to a source; a non-transitory machine-readable medium that stores instructions that, when executed by the set of processors, cause said processors to perform operations comprising: identifying a plurality of receivers that are requesting to receive data from the source in a session; sending a set of one or more PATH messages to one or more nodes downstream of the source edge router to signal a plurality of separate point-to-point label switched paths (LSPs) between the source edge router and a plurality of receiver edge routers associated with the plurality of receivers, wherein each one of the set of PATH messages includes a same identifier of a point-to-multipoint (P2MP) LSP that includes a session object that contains a tunnel identifier and a P2MP identifier; and receiving, from each of the one or more nodes downstream of the source edge router, a set of one or more RESV messages, wherein each one of the received RESV messages includes the identifier of the P2MP LSP and a label allocated by that downstream node that is to be used by the source edge router when sending traffic of the P2MP LSP to that downstream node.

14. The apparatus of claim 13 , wherein the non-transitory machine-readable medium further stores instructions that, when executed by the set of processors, cause said set of processors to further perform operations comprising: creating a mapping of an IP address associated with the P2MP LSP and the one or more labels specified in the set of received RESV messages.

15. The apparatus of claim 14 , wherein the non-transitory machine-readable medium further stores instructions that, when executed by the set of processors, cause said set of processors to further perform operations comprising: identifying another receiver that is requesting to receive data from the source in the session; sending a PATH message to signal a point-to-point LSP for the another receiver, wherein the PATH message includes the identifier of the P2MP LSP; receiving a RESV message that includes the identifier of the P2MP LSP and a label; responsive to determining that the label specified in the RESV message is not already associated with the P2MP LSP, adding that label to the mapping of the IP address associated with the P2MP LSP.

16. The apparatus of claim 13 , wherein the non-transitory machine-readable medium further stores instructions that, when executed by the set of processors, cause said set of processors to further perform operations comprising: prior to sending the set of PATH messages, computing a separate point-to-point LSP between the source edge router and each of the plurality of receiver edge routers.

17. The apparatus of claim 16 , wherein the separate point-to-point LSPs are computed to share resources where possible as determined by an IP routing protocol with Traffic Engineering (TE) extensions.

18. The apparatus of claim 14 , wherein the non-transitory machine-readable medium further stores instructions that, when executed by the set of processors, cause said set of processors to further perform operations comprising: determining that one of the plurality of receivers is to be removed from the session; sending a PATH TEAR message to the one of the set of downstream nodes to reach the receiver that is to be removed from the session, wherein the PATH TEAR message identifies a point-to-point LSP to remove and includes the identifier of the P2MP LSP to cause the point-to-point LSP for the receiver to be removed from the P2MP LSP.

19. The apparatus of claim 18 , wherein the non-transitory machine-readable medium further stores instructions that, when executed by the set of processors, cause said set of processors to further perform operations comprising: responsive to determining that the one of the set of downstream nodes is involved only in a route to the receiver being removed, removing the label allocated by that downstream node from the mapping of the IP address associated with the P2MP LSP.

20. An apparatus, comprising: a set of one or more processors of a core router; a non-transitory machine-readable medium that stores instructions that, when executed by the set of processors, cause said processors to perform operations comprising: receiving a set of one or more first PATH messages from an upstream node, wherein the set of first PATH messages identify at least a portion of a first point-to-point label switched path (LSP) between a source edge router and a first receiver edge router and identify at least a portion of a second point-to-point LSP between the source edge router and a second receiver edge router, wherein the set of first PATH messages each includes a same identifier of a point-to-multipoint (P2MP) LSP that includes a session object that contains a tunnel identifier and a P2MP identifier; sending a second PATH message to a first downstream node on the first point-to-point LSP, the second PATH message including the identifier of the P2MP LSP; sending a third PATH message to a second downstream node on the second point-to-point LSP, the third PATH message including the identifier of the P2MP LSP; receiving, from the first downstream node, a first RESV message responsive to the second PATH message, the first RESV message including the identifier of the P2MP LSP and a first label allocated by the first downstream node; receiving, from the second downstream node, a second RESV message responsive to the third PATH message, the second RESV message including the identifier of the P2MP LSP and a second label allocated by the second downstream node; allocating a third label to be used by the upstream node when transmitting packets for the P2MP LSP to the core router; mapping the third label with the first label and the second label to enable the core router to replicate packets that are received from the upstream node that are labeled with the third label, send each replicated packet to the first downstream node being labeled with the first label, and send each replicated packet to the second downstream node being labeled with the second label; and sending a set of one or more third RESV messages to the upstream node responsive to receiving the first RESV message and the second RESV message, wherein the set of third RESV messages each includes the identifier of the P2MP LSP and the third label.

21. The apparatus of claim 20 , wherein the non-transitory machine-readable medium further stores instructions that, when executed by the set of processors, cause said set of processors to further perform operations comprising: receiving a packet from the upstream node labeled with the third label; labeling the packet with the first label; sending the packet labeled with the first label to the first downstream node; labeling the packet with the second label; and sending the packet labeled with the second label to the second downstream node.

22. The apparatus of claim 20 , wherein the upstream node is the source edge router attached to a source.

23. The apparatus of claim 20 , wherein the upstream node is another core router.

24. The apparatus of claim 20 , wherein the non-transitory machine-readable medium further stores instructions that, when executed by the set of processors, cause said set of processors to further perform operations comprising: receiving a fourth PATH message from the upstream node, wherein the fourth PATH message identifies at least a portion of a third point-to-point LSP between the source edge router and a third receiver edge router, wherein the fourth PATH message includes the identifier of the P2MP LSP, and wherein a path of the third point-to-point LSP shares a same link between the core router and the first downstream node; sending a fifth PATH message to the first downstream node, wherein the fifth PATH message includes the identifier of the P2MP LSP; receiving, from the first downstream node, a fourth RESV message responsive to the fifth PATH message, the fourth RESV message including the identifier of the P2MP LSP and the first label; and sending a fifth RESV message to the upstream node responsive to receiving the fourth RESV message, wherein the fifth RESV message includes the identifier of the P2MP LSP and the third label.